Code sample small fixes (#70343)

packages/flutter/lib/src/material/tooltip.dart

@@ -34,13 +34,14 @@ import 'tooltip_theme.dart';
 ///
 /// This example show a basic [Tooltip] which has a [Text] as child.
 /// [message] contains your label to be shown by the tooltip when
-/// the child that Tooltip wraps is long pressed.
+/// the child that Tooltip wraps is hovered over on web or desktop. On mobile,
+/// the tooltip is shown when the widget is long pressed.
 ///
 /// ```dart
 /// Widget build(BuildContext context) {
 ///   return Tooltip(
 ///     message: "I am a Tooltip",
-///     child: Text("Tap this text and hold down to show a tooltip."),
+///     child: Text("Hover over the text to show a tooltip."),
 ///   );
 /// }
 /// ```

packages/flutter/lib/src/widgets/basic.dart

@@ -1474,7 +1474,7 @@ class CompositedTransformFollower extends SingleChildRenderObjectWidget {
 ///
 /// {@youtube 560 315 https://www.youtube.com/watch?v=T4Uehk3_wlY}
 ///
-/// {@tool sample --template=stateless_widget_scaffold_center}
+/// {@tool dartpad --template=stateless_widget_scaffold_center}
 ///
 /// In this example, the image is stretched to fill the entire [Container], which would
 /// not happen normally without using FittedBox.

packages/flutter/lib/src/widgets/dismissible.dart

@@ -68,7 +68,8 @@ enum DismissDirection {
 /// {@tool dartpad --template=stateful_widget_scaffold}
 ///
 /// This sample shows how you can use the [Dismissible] widget to
-/// remove list items using swipe gestures.
+/// remove list items using swipe gestures. Swipe any of the list
+/// tiles to the left or right to dismiss them from the [ListView].
 ///
 /// ```dart
 /// List<int> items = List<int>.generate(100, (index) => index);

packages/flutter/lib/src/widgets/drag_target.dart

@@ -99,7 +99,7 @@ enum DragAnchor {
 ///
 /// {@youtube 560 315 https://www.youtube.com/watch?v=QzA4c4QHZCY}
 ///
-/// {@tool dartpad --template=stateful_widget_material}
+/// {@tool dartpad --template=stateful_widget_scaffold}
 ///
 /// The following example has a [Draggable] widget along with a [DragTarget]
 /// in a row demonstrating an incremented `acceptedData` integer value when

packages/flutter/lib/src/widgets/shortcuts.dart

@@ -424,10 +424,18 @@ class ShortcutManager extends ChangeNotifier with Diagnosticable {
 ///       child: Focus(
 ///         autofocus:true,
 ///         child: Column(
+///           mainAxisAlignment: MainAxisAlignment.center,
 ///           children: <Widget>[
-///             Text('Add to the counter by pressing keyboard Shift and keyboard "K"'),
-///             Text('Subtract from the counter by pressing keyboard Shift and keyboard "L"'),
-///             Text('count: $count'),
+///             Text('Add: keyboard Shift + "k"'),
+///             Text('Subtract: keyboard Shift + "l"'),
+///             SizedBox(height: 10.0),
+///             ColoredBox(
+///               color: Colors.yellow,
+///               child: Padding(
+///                 padding: EdgeInsets.all(4.0),
+///                 child: Text('count: $count'),
+///               ),
+///             ),
 ///           ],
 ///         ),
 ///       ),